Method of forming a security document

Abstract

A method of forming a security document includes: providing a security document substrate, the security document substrate including a security device including a colour shifting element and a light control layer covering at least a part of the colour shifting element, wherein the light control layer has a surface structure including one or more elevations and depressions that modifies the angle of light from the colour shifting element to generate a first optical effect, and; selectively modifying a part of the light control layer so as to generate a second optical effect different from the first optical effect.

1 - 45 . (canceled) 
     
     
         46 . A method of forming a security document, comprising:
 (i) providing a security document substrate, the security document substrate comprising a security device comprising a colour shifting element and a light control layer covering at least a part of the colour shifting element, wherein the light control layer has a surface structure comprising one or more elevations and depressions that modifies the angle of light from the colour shifting element to generate a first optical effect, and;   (ii) selectively modifying a part of the light control layer so as to generate a second optical effect different from the first optical effect.   
     
     
         47 . The method of  claim 46  wherein, at least at one viewing angle, the first optical effect exhibits a first colour, and the second optical effect exhibits a second colour different from the first colour. 
     
     
         48 . The method of  claim 46 , wherein the second optical effect is the optical effect generated by the colour shifting element in the absence of a light control layer. 
     
     
         49 . The method of  claim 46 , wherein the selectively modifying comprises introducing a material to a part of the light control layer. 
     
     
         50 . The method of  claim 49 , wherein the material has a refractive index substantially the same as that of the light control layer. 
     
     
         51 . The method of  claim 49 , wherein the material is a printable resin and wherein the printable resin is selectively introduced to a part of the light control layer by digital printing, preferably inkjet printing or laser printing. 
     
     
         52 . The method of  claim 49 , wherein the material is a varnish. 
     
     
         53 . The method of  claim 46 , wherein the selectively modifying comprises removing at least a part of the light control layer such that no light control layer is present at that part of the security device. 
     
     
         54 . The method of  claim 46 , wherein the selectively modifying comprises deforming at least a part of the light control layer. 
     
     
         55 . The method of  claim 46 , wherein the light control layer comprises a microprismatic structure, wherein the microprismatic structure comprises a plurality of microprisms. 
     
     
         56 . The method of  claim 55 , wherein the microprismatic structure comprises an array of linear microprisms. 
     
     
         57 . The method of  claim 56 , wherein the microprismatic structure comprises two or more arrays of linear microprisms, wherein the long axes of one array are angularly offset from the axes of the other array. 
     
     
         58 . The method of  claim 55 , wherein the microprismatic structure is either a one-dimensional microprismatic structure or a two-dimensional microprismatic structure. 
     
     
         59 . The method of  claim 46 , wherein the light control layer is selectively modified so as to define indicia on the light control layer. 
     
     
         60 . The method of  claim 59 , wherein the light control layer is selectively modified so as to define a pattern related to the security document, and wherein pattern is unique to the security document. 
     
     
         61 . The method of  claim 59 , wherein the light control layer is selectively modified so as to define biometric data related to the owner of the security document. 
     
     
         62 . The method of  claim 46 , wherein the light control layer is selectively modified so as to define first and second regions of the light control layer, wherein the first and second regions provide different optical effects. 
     
     
         63 . The method of  claim 46 , wherein the security document is a passport, banknote, security label, identification card, driving license or other document of value. 
     
     
         64 . The method of  claim 46 , wherein the colour shifting element comprises one of: a photonic crystal structure, a liquid crystal material, an interference pigment, a pearlescent pigment, a structured interference material, or a thin film interference structure such as a Bragg stack. 
     
     
         65 . A security document formed by the method of  claim 46 . 
     
     
         66 . The security document of  claim 65 , wherein the security document is a passport, and the light control layer is selectively modified so as to define biometric data relating to the passport holder.